Added description text to the File Encoding list
Added description text to the File Encoding list

I updated the list of text encodings that appear in the Settings configuration menu to properly reflect the code pages supported by [encoding-selector](https://github.com/atom/encoding-selector), as well as present descriptive text in the selection menu.

In the process, I removed what appeared to be a duplicate entry ('iso88597').

Note: I don't know if this change will affect the functionality of the menu, but I presume a more experience coder can figure this out.
AdrianVovk/substance-ide,stinsonga/atom,AdrianVovk/substance-ide,tjkr/atom,rlugojr/atom,xream/atom,decaffeinate-examples/atom,CraZySacX/atom,sotayamashita/atom,kevinrenaers/atom,PKRoma/atom,t9md/atom,atom/atom,atom/atom,brettle/atom,brettle/atom,sotayamashita/atom,CraZySacX/atom,Mokolea/atom,stinsonga/atom,stinsonga/atom,AlexxNica/atom,kevinrenaers/atom,ardeshirj/atom,Arcanemagus/atom,FIT-CSE2410-A-Bombs/atom,Mokolea/atom,AdrianVovk/substance-ide,Arcanemagus/atom,tjkr/atom,decaffeinate-examples/atom,ardeshirj/atom,andrewleverette/atom,t9md/atom,AlexxNica/atom,PKRoma/atom,ardeshirj/atom,AlexxNica/atom,Arcanemagus/atom,andrewleverette/atom,stinsonga/atom,liuderchi/atom,FIT-CSE2410-A-Bombs/atom,xream/atom,CraZySacX/atom,decaffeinate-examples/atom,rlugojr/atom,andrewleverette/atom,brettle/atom,tjkr/atom,liuderchi/atom,xream/atom,sotayamashita/atom,rlugojr/atom,Mokolea/atom,atom/atom,liuderchi/atom,kevinrenaers/atom,liuderchi/atom,t9md/atom,FIT-CSE2410-A-Bombs/atom,PKRoma/atom,decaffeinate-examples/atom